1. Field of the Invention
The present invention relates to apparatus for use in lamination and/or encapsulation processes. More particularly, this invention pertains to durable apparatus of economical structure for the lamination of relatively large surface area workpieces.
2. Description of the Prior Art
In the lamination art pressure and heat must interact in preferred ways in a controlled environment to provide an acceptable product. Prior art lamination apparatus has often included, as means for applying pressure across the workpiece surface, an elastomeric membrane in conjunction with a vacuum pump or the like. By providing a sealable relationship between the membrane and an underlying base upon which the workpiece to be laminated is placed and thereafter evacuating air from beneath the membrane, atmospheric pressure (approximately 15 ps.i. at sea level) is exerted across the surface of the workpiece through the membrane. This principle and basic apparatus therefor are disclosed, for example, in U.S. Pat. No. 4,287,015 of Danner, Jr. for "Vacuum Bag Used in Making Laminated Products".
While the vacuum bag principle has been well accepted in the lamination and encapsulation arts, the realization of apparatus for the lamination of workpieces having relatively large surface areas, such as solar cell panels, introduces significant problems that are not experienced in the manufacture of smaller objects. The utilization of atmospheric pressure in combination with a vacuum to generate forces for the lamination of objects of relatively large surface areas submits the laminating apparatus which supports the workpiece to large stresses. This is due to the large surface area of the lamination apparatus necessarily required to accommodate the large workpiece. Thus, large area laminator design requires resistance to forces that can fatigue the apparatus itself and degrade the quality of laminated product.
Design is complicated by an accompanying requirement that the lamination apparatus be compatible with means for applying a suitable temperature profile to the workpiece before, during and, often, immediately after the lamination process. Both radiant and conduction heating are conventionally employed in conjunction with lamination processes, and, in accordance with the facilities of the user, such heating may be accomplished internal or external to the lamination apparatus. The application of heat from an external source may be accomplished by placing the lamination apparatus into an autoclave or other oven. A heat blanket provides an advantageous means for conduction heating of the workpiece. However, to be effective the lamination apparatus must provide a design whereby the blanket can be mounted adjacent the workpiece for efficient heating.
The careful control of workpiece temperature profile requires effective heat transfer through the apparatus which supports the workpiece. In the event that an external heat source is employed, a laminator having good heat transfer properties allows the workpiece to be heated with a minimal energy input. Achievement of an oftentimes-critical optimum cooling profile for the workpiece is enhanced when the surrounding structures do not include members having unnecessarily large masses that can function as heat storage and absorption areas.
Thus, the effective lamination of relatively large area workpieces has created a current need in the art for apparatus of sufficient strength to withstand considerable force without impairing heat transfer capabilities and other aspects essential to the lamination process.